Rocks formed by the accumulation and compaction of sediment.
sedimentary rocks
Forces inside the Earth that cause a rock change into another type, without melting.
metamorphic rocks
These rocks are formed from cooled magma.
magmatic (or igneous) rocks
The melted, rocky material formed below the Earth´s crust or mantle.
magma
A type of igneous rock that forms as magma cools slowly under the ground over thousands of years. As a result, the mineral crystals are large and well done.
plutonic (intrusive) rocks
A type of igneous rock that forms as lava cools rapidly on the surface of the Earth. As a result, the mineral crystals are tiny.
volcanic (extrusive) rocks
A plutonic igneous rock with large, visible crystals. It is the most common rock in the continental crust and is very hard and strong.
granite
A volcanic igneous rock that is dark or black in color. It is heavy and hard and is the most common rock on the ocean floor.
basalt
A volcanic igneous rock that is mostly light in color. It is lightweight and floats in water. It has a spongy texture from bubble holes.
pumice
A volcanic igneous rock that is black and smooth. It looks like black glass and its edges can cut.
obsidian
A metamorphic rock that is usually black and slightly shiny because of the presence of mica. It is hard but can be separated into thin layers or sheets.
slate
A metamorphic rock that can be many different colors, often with veins. It does not separate into layers.
marble
